Prevent CH4 overflow

Fix Arduino lint errors and bump library version

docs/issues.md

@@ -5,10 +5,12 @@ Este documento resume los problemas reportados en el repositorio y las solucione
 ## Abiertos
 
 ### #75 MQ-3 sensor and CH4 gas reading 'ovf' failure
-**Estado:** abierto
+**Estado:** resuelto en la rama `main`
 
 El usuario reporta desbordamiento ("ovf") al utilizar valores muy altos en `setA` y `setB` para leer CH4 con un sensor MQ-3. La solución propuesta es revisar los valores utilizados en `setA` y `setB`, ya que `2*10^31` en C++ no corresponde a `2e31`. Se recomienda usar notación exponencial (`2e31`) o `pow(10,31)` y comprobar que los parámetros no excedan el rango de `float`.
 
+**Actualización:** se añadieron validaciones de entrada, predicción de desbordamiento mediante logaritmos y verificación del resultado final para evitar valores "ovf" incluso con coeficientes muy altos. Las nuevas funciones limitan `setA` y `setB` y emplean cálculos en doble precisión.
+
 ### #74 possible error in the calculation formula for `_RS_Calc`
 **Estado:** resuelto en la rama `work`
 

examples/Alcoholimeter/Alcoholimeter.ino

@@ -66,7 +66,7 @@ void setup() {
   // Explanation: 
    // In this routine the sensor will measure the resistance of the sensor supposedly before being pre-heated
   // and on clean air (Calibration conditions), setting up R0 value.
-  // We recomend executing this routine only on setup in laboratory conditions.
+  // We recommend executing this routine only on setup in laboratory conditions.
   // This routine does not need to be executed on each restart, you can load your R0 value from eeprom.
   // Acknowledgements: https://jayconsystems.com/blog/understanding-a-gas-sensor
   Serial.print("Calibrating please wait.");
@@ -80,8 +80,8 @@ void setup() {
   MQ3.setR0(calcR0/10);
   Serial.println("  done!.");
   
-  if(isinf(calcR0)) {Serial.println("Warning: Conection issue, R0 is infinite (Open circuit detected) please check your wiring and supply"); while(1);}
-  if(calcR0 == 0){Serial.println("Warning: Conection issue found, R0 is zero (Analog pin shorts to ground) please check your wiring and supply"); while(1);}
+  if(isinf(calcR0)) {Serial.println("Warning: Connection issue, R0 is infinite (Open circuit detected) please check your wiring and supply"); while(1);}
+  if(calcR0 == 0){Serial.println("Warning: Connection issue found, R0 is zero (Analog pin shorts to ground) please check your wiring and supply"); while(1);}
   /*****************************  MQ CAlibration ********************************************/  
 }
 

examples/ESP32/ESP32.ino

@@ -65,7 +65,7 @@ void setup() {
   // Explanation: 
    // In this routine the sensor will measure the resistance of the sensor supposedly before being pre-heated
   // and on clean air (Calibration conditions), setting up R0 value.
-  // We recomend executing this routine only on setup in laboratory conditions.
+  // We recommend executing this routine only on setup in laboratory conditions.
   // This routine does not need to be executed on each restart, you can load your R0 value from eeprom.
   // Acknowledgements: https://jayconsystems.com/blog/understanding-a-gas-sensor
   Serial.print("Calibrating please wait.");
@@ -79,8 +79,8 @@ void setup() {
   MQ3.setR0(calcR0/10);
   Serial.println("  done!.");
   
-  if(isinf(calcR0)) {Serial.println("Warning: Conection issue, R0 is infinite (Open circuit detected) please check your wiring and supply"); while(1);}
-  if(calcR0 == 0){Serial.println("Warning: Conection issue found, R0 is zero (Analog pin shorts to ground) please check your wiring and supply"); while(1);}
+  if(isinf(calcR0)) {Serial.println("Warning: Connection issue, R0 is infinite (Open circuit detected) please check your wiring and supply"); while(1);}
+  if(calcR0 == 0){Serial.println("Warning: Connection issue found, R0 is zero (Analog pin shorts to ground) please check your wiring and supply"); while(1);}
   /*****************************  MQ CAlibration ********************************************/ 
   MQ3.serialDebug(true);
 }

examples/ESP32/ESP32_WROOM_32D/ESP32_WROOM_32D.ino

@@ -86,7 +86,7 @@ void setup()
   // Explanation: 
    // In this routine the sensor will measure the resistance of the sensor supposedly before being pre-heated
   // and on clean air (Calibration conditions), setting up R0 value.
-  // We recomend executing this routine only on setup in laboratory conditions.
+  // We recommend executing this routine only on setup in laboratory conditions.
   // This routine does not need to be executed on each restart, you can load your R0 value from eeprom.
   // Acknowledgements: https://jayconsystems.com/blog/understanding-a-gas-sensor
   Serial.print("Calibrating please wait.");
@@ -100,8 +100,8 @@ void setup()
   MQ2.setR0(calcR0/10);
   Serial.println("  done!.");
   
-  if(isinf(calcR0)) {Serial.println("Warning: Conection issue, R0 is infinite (Open circuit detected) please check your wiring and supply"); while(1);}
-  if(calcR0 == 0){Serial.println("Warning: Conection issue found, R0 is zero (Analog pin shorts to ground) please check your wiring and supply"); while(1);}
+  if(isinf(calcR0)) {Serial.println("Warning: Connection issue, R0 is infinite (Open circuit detected) please check your wiring and supply"); while(1);}
+  if(calcR0 == 0){Serial.println("Warning: Connection issue found, R0 is zero (Analog pin shorts to ground) please check your wiring and supply"); while(1);}
   /*****************************  MQ CAlibration ********************************************/ 
   //MQ2.serialDebug(true); uncomment if you want to print the table on the serial port
 

examples/ESP8266/ESP8266.ino

@@ -65,7 +65,7 @@ void setup() {
   // Explanation: 
    // In this routine the sensor will measure the resistance of the sensor supposedly before being pre-heated
   // and on clean air (Calibration conditions), setting up R0 value.
-  // We recomend executing this routine only on setup in laboratory conditions.
+  // We recommend executing this routine only on setup in laboratory conditions.
   // This routine does not need to be executed on each restart, you can load your R0 value from eeprom.
   // Acknowledgements: https://jayconsystems.com/blog/understanding-a-gas-sensor
   Serial.print("Calibrating please wait.");
@@ -79,8 +79,8 @@ void setup() {
   MQ3.setR0(calcR0/10);
   Serial.println("  done!.");
   
-  if(isinf(calcR0)) {Serial.println("Warning: Conection issue, R0 is infinite (Open circuit detected) please check your wiring and supply"); while(1);}
-  if(calcR0 == 0){Serial.println("Warning: Conection issue found, R0 is zero (Analog pin shorts to ground) please check your wiring and supply"); while(1);}
+  if(isinf(calcR0)) {Serial.println("Warning: Connection issue, R0 is infinite (Open circuit detected) please check your wiring and supply"); while(1);}
+  if(calcR0 == 0){Serial.println("Warning: Connection issue found, R0 is zero (Analog pin shorts to ground) please check your wiring and supply"); while(1);}
   /*****************************  MQ CAlibration ********************************************/ 
   MQ3.serialDebug(true);
 }

examples/LinearVsExponential/LinearVsExponential.ino

@@ -45,7 +45,7 @@ void setup() {
   // Explanation: 
    // In this routine the sensor will measure the resistance of the sensor supposedly before being pre-heated
   // and on clean air (Calibration conditions), setting up R0 value.
-  // We recomend executing this routine only on setup in laboratory conditions.
+  // We recommend executing this routine only on setup in laboratory conditions.
   // This routine does not need to be executed on each restart, you can load your R0 value from eeprom.
   // Acknowledgements: https://jayconsystems.com/blog/understanding-a-gas-sensor
   Serial.print("Calibrating please wait.");
@@ -59,8 +59,8 @@ void setup() {
   MQ4.setR0(calcR0/10);
   Serial.println("  done!.");
   
-  if(isinf(calcR0)) {Serial.println("Warning: Conection issue, R0 is infinite (Open circuit detected) please check your wiring and supply"); while(1);}
-  if(calcR0 == 0){Serial.println("Warning: Conection issue found, R0 is zero (Analog pin shorts to ground) please check your wiring and supply"); while(1);}
+  if(isinf(calcR0)) {Serial.println("Warning: Connection issue, R0 is infinite (Open circuit detected) please check your wiring and supply"); while(1);}
+  if(calcR0 == 0){Serial.println("Warning: Connection issue found, R0 is zero (Analog pin shorts to ground) please check your wiring and supply"); while(1);}
   /*****************************  MQ CAlibration ********************************************/ 
 
   /* 

examples/MQ-131/MQ-131.ino

@@ -67,7 +67,7 @@ void setup() {
   // Explanation: 
    // In this routine the sensor will measure the resistance of the sensor supposedly before being pre-heated
   // and on clean air (Calibration conditions), setting up R0 value.
-  // We recomend executing this routine only on setup in laboratory conditions.
+  // We recommend executing this routine only on setup in laboratory conditions.
   // This routine does not need to be executed on each restart, you can load your R0 value from eeprom.
   // Acknowledgements: https://jayconsystems.com/blog/understanding-a-gas-sensor
   Serial.print("Calibrating please wait.");
@@ -81,8 +81,8 @@ void setup() {
   MQ131.setR0(calcR0/10);
   Serial.println("  done!.");
   
-  if(isinf(calcR0)) {Serial.println("Warning: Conection issue, R0 is infinite (Open circuit detected) please check your wiring and supply"); while(1);}
-  if(calcR0 == 0){Serial.println("Warning: Conection issue found, R0 is zero (Analog pin shorts to ground) please check your wiring and supply"); while(1);}
+  if(isinf(calcR0)) {Serial.println("Warning: Connection issue, R0 is infinite (Open circuit detected) please check your wiring and supply"); while(1);}
+  if(calcR0 == 0){Serial.println("Warning: Connection issue found, R0 is zero (Analog pin shorts to ground) please check your wiring and supply"); while(1);}
   /*****************************  MQ CAlibration ********************************************/ 
   MQ131.serialDebug(true);
   Serial.println("Ignore Ratio = RS/R0, for this example we will use readSensorR0Rs, the ratio calculated will be R0/Rs. Thanks :)");

examples/MQ-135-ALL/MQ-135-ALL.ino

@@ -55,7 +55,7 @@ void setup() {
   // Explanation: 
   // In this routine the sensor will measure the resistance of the sensor supposedly before being pre-heated
   // and on clean air (Calibration conditions), setting up R0 value.
-  // We recomend executing this routine only on setup in laboratory conditions.
+  // We recommend executing this routine only on setup in laboratory conditions.
   // This routine does not need to be executed on each restart, you can load your R0 value from eeprom.
   // Acknowledgements: https://jayconsystems.com/blog/understanding-a-gas-sensor
   Serial.print("Calibrating please wait.");
@@ -69,8 +69,8 @@ void setup() {
   MQ135.setR0(calcR0/10);
   Serial.println("  done!.");
   
-  if(isinf(calcR0)) {Serial.println("Warning: Conection issue, R0 is infinite (Open circuit detected) please check your wiring and supply"); while(1);}
-  if(calcR0 == 0){Serial.println("Warning: Conection issue found, R0 is zero (Analog pin shorts to ground) please check your wiring and supply"); while(1);}
+  if(isinf(calcR0)) {Serial.println("Warning: Connection issue, R0 is infinite (Open circuit detected) please check your wiring and supply"); while(1);}
+  if(calcR0 == 0){Serial.println("Warning: Connection issue found, R0 is zero (Analog pin shorts to ground) please check your wiring and supply"); while(1);}
   /*****************************  MQ CAlibration ********************************************/ 
   Serial.println("** Values from MQ-135 ****");
   Serial.println("|    CO   |  Alcohol |   CO2  |  Toluen  |  NH4  |  Aceton  |");  

examples/MQ-135-CorrectionFactorDHT11/MQ-135-CorrectionFactorDHT11.ino

@@ -106,7 +106,7 @@ void setup() {
   // Explanation: 
    // In this routine the sensor will measure the resistance of the sensor supposedly before being pre-heated
   // and on clean air (Calibration conditions), setting up R0 value.
-  // We recomend executing this routine only on setup in laboratory conditions.
+  // We recommend executing this routine only on setup in laboratory conditions.
   // This routine does not need to be executed on each restart, you can load your R0 value from eeprom.
   // Acknowledgements: https://jayconsystems.com/blog/understanding-a-gas-sensor
   Serial.print("Calibrating please wait.");
@@ -120,8 +120,8 @@ void setup() {
   MQ135.setR0(calcR0/10);
   Serial.println("  done!.");
   
-  if(isinf(calcR0)) {Serial.println("Warning: Conection issue, R0 is infinite (Open circuit detected) please check your wiring and supply"); while(1);}
-  if(calcR0 == 0){Serial.println("Warning: Conection issue found, R0 is zero (Analog pin shorts to ground) please check your wiring and supply"); while(1);}
+  if(isinf(calcR0)) {Serial.println("Warning: Connection issue, R0 is infinite (Open circuit detected) please check your wiring and supply"); while(1);}
+  if(calcR0 == 0){Serial.println("Warning: Connection issue found, R0 is zero (Analog pin shorts to ground) please check your wiring and supply"); while(1);}
   /*****************************  MQ CAlibration ********************************************/ 
   MQ135.serialDebug(true);
   // Set delay between sensor readings based on sensor details.

examples/MQ-135/MQ-135.ino

@@ -67,7 +67,7 @@ void setup() {
   // Explanation: 
    // In this routine the sensor will measure the resistance of the sensor supposedly before being pre-heated
   // and on clean air (Calibration conditions), setting up R0 value.
-  // We recomend executing this routine only on setup in laboratory conditions.
+  // We recommend executing this routine only on setup in laboratory conditions.
   // This routine does not need to be executed on each restart, you can load your R0 value from eeprom.
   // Acknowledgements: https://jayconsystems.com/blog/understanding-a-gas-sensor
   Serial.print("Calibrating please wait.");
@@ -81,8 +81,8 @@ void setup() {
   MQ135.setR0(calcR0/10);
   Serial.println("  done!.");
   
-  if(isinf(calcR0)) {Serial.println("Warning: Conection issue, R0 is infinite (Open circuit detected) please check your wiring and supply"); while(1);}
-  if(calcR0 == 0){Serial.println("Warning: Conection issue found, R0 is zero (Analog pin shorts to ground) please check your wiring and supply"); while(1);}
+  if(isinf(calcR0)) {Serial.println("Warning: Connection issue, R0 is infinite (Open circuit detected) please check your wiring and supply"); while(1);}
+  if(calcR0 == 0){Serial.println("Warning: Connection issue found, R0 is zero (Analog pin shorts to ground) please check your wiring and supply"); while(1);}
   /*****************************  MQ CAlibration ********************************************/ 
   MQ135.serialDebug(true);
 }

examples/MQ-136/MQ-136.ino

@@ -60,7 +60,7 @@ void setup() {
   // Explanation: 
    // In this routine the sensor will measure the resistance of the sensor supposedly before being pre-heated
   // and on clean air (Calibration conditions), setting up R0 value.
-  // We recomend executing this routine only on setup in laboratory conditions.
+  // We recommend executing this routine only on setup in laboratory conditions.
   // This routine does not need to be executed on each restart, you can load your R0 value from eeprom.
   // Acknowledgements: https://jayconsystems.com/blog/understanding-a-gas-sensor
   Serial.print("Calibrating please wait.");
@@ -74,8 +74,8 @@ void setup() {
   MQ136.setR0(calcR0/10);
   Serial.println("  done!.");
   
-  if(isinf(calcR0)) {Serial.println("Warning: Conection issue, R0 is infinite (Open circuit detected) please check your wiring and supply"); while(1);}
-  if(calcR0 == 0){Serial.println("Warning: Conection issue found, R0 is zero (Analog pin shorts to ground) please check your wiring and supply"); while(1);}
+  if(isinf(calcR0)) {Serial.println("Warning: Connection issue, R0 is infinite (Open circuit detected) please check your wiring and supply"); while(1);}
+  if(calcR0 == 0){Serial.println("Warning: Connection issue found, R0 is zero (Analog pin shorts to ground) please check your wiring and supply"); while(1);}
   /*****************************  MQ CAlibration ********************************************/ 
   MQ136.serialDebug(true);
 }

examples/MQ-2/MQ-2.ino

@@ -64,7 +64,7 @@ void setup() {
   // Explanation: 
    // In this routine the sensor will measure the resistance of the sensor supposedly before being pre-heated
   // and on clean air (Calibration conditions), setting up R0 value.
-  // We recomend executing this routine only on setup in laboratory conditions.
+  // We recommend executing this routine only on setup in laboratory conditions.
   // This routine does not need to be executed on each restart, you can load your R0 value from eeprom.
   // Acknowledgements: https://jayconsystems.com/blog/understanding-a-gas-sensor
   Serial.print("Calibrating please wait.");
@@ -78,8 +78,8 @@ void setup() {
   MQ2.setR0(calcR0/10);
   Serial.println("  done!.");
   
-  if(isinf(calcR0)) {Serial.println("Warning: Conection issue, R0 is infinite (Open circuit detected) please check your wiring and supply"); while(1);}
-  if(calcR0 == 0){Serial.println("Warning: Conection issue found, R0 is zero (Analog pin shorts to ground) please check your wiring and supply"); while(1);}
+  if(isinf(calcR0)) {Serial.println("Warning: Connection issue, R0 is infinite (Open circuit detected) please check your wiring and supply"); while(1);}
+  if(calcR0 == 0){Serial.println("Warning: Connection issue found, R0 is zero (Analog pin shorts to ground) please check your wiring and supply"); while(1);}
   /*****************************  MQ CAlibration ********************************************/ 
 
   MQ2.serialDebug(true);

examples/MQ-3/MQ-3.ino

@@ -66,7 +66,7 @@ void setup() {
   // Explanation: 
    // In this routine the sensor will measure the resistance of the sensor supposedly before being pre-heated
   // and on clean air (Calibration conditions), setting up R0 value.
-  // We recomend executing this routine only on setup in laboratory conditions.
+  // We recommend executing this routine only on setup in laboratory conditions.
   // This routine does not need to be executed on each restart, you can load your R0 value from eeprom.
   // Acknowledgements: https://jayconsystems.com/blog/understanding-a-gas-sensor
   Serial.print("Calibrating please wait.");
@@ -80,8 +80,8 @@ void setup() {
   MQ3.setR0(calcR0/10);
   Serial.println("  done!.");
   
-  if(isinf(calcR0)) {Serial.println("Warning: Conection issue, R0 is infinite (Open circuit detected) please check your wiring and supply"); while(1);}
-  if(calcR0 == 0){Serial.println("Warning: Conection issue found, R0 is zero (Analog pin shorts to ground) please check your wiring and supply"); while(1);}
+  if(isinf(calcR0)) {Serial.println("Warning: Connection issue, R0 is infinite (Open circuit detected) please check your wiring and supply"); while(1);}
+  if(calcR0 == 0){Serial.println("Warning: Connection issue found, R0 is zero (Analog pin shorts to ground) please check your wiring and supply"); while(1);}
   /*****************************  MQ CAlibration ********************************************/ 
   MQ3.serialDebug(true);
 }

examples/MQ-303A/MQ-303A.ino

@@ -64,7 +64,7 @@ void setup() {
   // Explanation: 
    // In this routine the sensor will measure the resistance of the sensor supposedly before being pre-heated
   // and on clean air (Calibration conditions), setting up R0 value.
-  // We recomend executing this routine only on setup in laboratory conditions.
+  // We recommend executing this routine only on setup in laboratory conditions.
   // This routine does not need to be executed on each restart, you can load your R0 value from eeprom.
   // Acknowledgements: https://jayconsystems.com/blog/understanding-a-gas-sensor
   Serial.print("Calibrating please wait.");
@@ -78,8 +78,8 @@ void setup() {
   MQ303.setR0(calcR0/10);
   Serial.println("  done!.");
   
-  if(isinf(calcR0)) {Serial.println("Warning: Conection issue, R0 is infinite (Open circuit detected) please check your wiring and supply"); while(1);}
-  if(calcR0 == 0){Serial.println("Warning: Conection issue found, R0 is zero (Analog pin shorts to ground) please check your wiring and supply"); while(1);}
+  if(isinf(calcR0)) {Serial.println("Warning: Connection issue, R0 is infinite (Open circuit detected) please check your wiring and supply"); while(1);}
+  if(calcR0 == 0){Serial.println("Warning: Connection issue found, R0 is zero (Analog pin shorts to ground) please check your wiring and supply"); while(1);}
   /*****************************  MQ CAlibration ********************************************/ 
   MQ303.serialDebug(true);
 }

examples/MQ-309A/MQ-309A.ino

@@ -67,7 +67,7 @@ void setup() {
   // Explanation: 
    // In this routine the sensor will measure the resistance of the sensor supposedly before being pre-heated
   // and on clean air (Calibration conditions), setting up R0 value.
-  // We recomend executing this routine only on setup in laboratory conditions.
+  // We recommend executing this routine only on setup in laboratory conditions.
   // This routine does not need to be executed on each restart, you can load your R0 value from eeprom.
   // Acknowledgements: https://jayconsystems.com/blog/understanding-a-gas-sensor
   Serial.print("Calibrating please wait.");
@@ -81,8 +81,8 @@ void setup() {
   MQ309.setR0(calcR0/10);
   Serial.println("  done!.");
   
-  if(isinf(calcR0)) {Serial.println("Warning: Conection issue, R0 is infinite (Open circuit detected) please check your wiring and supply"); while(1);}
-  if(calcR0 == 0){Serial.println("Warning: Conection issue found, R0 is zero (Analog pin shorts to ground) please check your wiring and supply"); while(1);}
+  if(isinf(calcR0)) {Serial.println("Warning: Connection issue, R0 is infinite (Open circuit detected) please check your wiring and supply"); while(1);}
+  if(calcR0 == 0){Serial.println("Warning: Connection issue found, R0 is zero (Analog pin shorts to ground) please check your wiring and supply"); while(1);}
   /*****************************  MQ CAlibration ********************************************/ 
   MQ309.serialDebug(true);
 }

examples/MQ-4-ALL/MQ-4-ALL.ino

@@ -55,7 +55,7 @@ void setup() {
   // Explanation: 
    // In this routine the sensor will measure the resistance of the sensor supposedly before being pre-heated
   // and on clean air (Calibration conditions), setting up R0 value.
-  // We recomend executing this routine only on setup in laboratory conditions.
+  // We recommend executing this routine only on setup in laboratory conditions.
   // This routine does not need to be executed on each restart, you can load your R0 value from eeprom.
   // Acknowledgements: https://jayconsystems.com/blog/understanding-a-gas-sensor
   Serial.print("Calibrating please wait.");
@@ -69,8 +69,8 @@ void setup() {
   MQ4.setR0(calcR0/10);
   Serial.println("  done!.");
   
-  if(isinf(calcR0)) {Serial.println("Warning: Conection issue, R0 is infinite (Open circuit detected) please check your wiring and supply"); while(1);}
-  if(calcR0 == 0){Serial.println("Warning: Conection issue found, R0 is zero (Analog pin shorts to ground) please check your wiring and supply"); while(1);}
+  if(isinf(calcR0)) {Serial.println("Warning: Connection issue, R0 is infinite (Open circuit detected) please check your wiring and supply"); while(1);}
+  if(calcR0 == 0){Serial.println("Warning: Connection issue found, R0 is zero (Analog pin shorts to ground) please check your wiring and supply"); while(1);}
   /*****************************  MQ CAlibration ********************************************/ 
 
   Serial.println("*************** Values from MQ-4 **********************");

examples/MQ-4-LINEAR/MQ-4-LINEAR.ino

@@ -54,7 +54,7 @@ void setup() {
   // Explanation: 
    // In this routine the sensor will measure the resistance of the sensor supposedly before being pre-heated
   // and on clean air (Calibration conditions), setting up R0 value.
-  // We recomend executing this routine only on setup in laboratory conditions.
+  // We recommend executing this routine only on setup in laboratory conditions.
   // This routine does not need to be executed on each restart, you can load your R0 value from eeprom.
   // Acknowledgements: https://jayconsystems.com/blog/understanding-a-gas-sensor
   Serial.print("Calibrating please wait.");
@@ -68,8 +68,8 @@ void setup() {
   MQ4.setR0(calcR0/10);
   Serial.println("  done!.");
   
-  if(isinf(calcR0)) {Serial.println("Warning: Conection issue, R0 is infinite (Open circuit detected) please check your wiring and supply"); while(1);}
-  if(calcR0 == 0){Serial.println("Warning: Conection issue found, R0 is zero (Analog pin shorts to ground) please check your wiring and supply"); while(1);}
+  if(isinf(calcR0)) {Serial.println("Warning: Connection issue, R0 is infinite (Open circuit detected) please check your wiring and supply"); while(1);}
+  if(calcR0 == 0){Serial.println("Warning: Connection issue found, R0 is zero (Analog pin shorts to ground) please check your wiring and supply"); while(1);}
   /*****************************  MQ CAlibration ********************************************/ 
 
   Serial.println("** Values from MQ-4**********");

examples/MQ-4/MQ-4.ino

@@ -65,7 +65,7 @@ void setup() {
   // Explanation: 
    // In this routine the sensor will measure the resistance of the sensor supposedly before being pre-heated
   // and on clean air (Calibration conditions), setting up R0 value.
-  // We recomend executing this routine only on setup in laboratory conditions.
+  // We recommend executing this routine only on setup in laboratory conditions.
   // This routine does not need to be executed on each restart, you can load your R0 value from eeprom.
   // Acknowledgements: https://jayconsystems.com/blog/understanding-a-gas-sensor
   Serial.print("Calibrating please wait.");
@@ -79,8 +79,8 @@ void setup() {
   MQ4.setR0(calcR0/10);
   Serial.println("  done!.");
   
-  if(isinf(calcR0)) {Serial.println("Warning: Conection issue, R0 is infinite (Open circuit detected) please check your wiring and supply"); while(1);}
-  if(calcR0 == 0){Serial.println("Warning: Conection issue found, R0 is zero (Analog pin shorts to ground) please check your wiring and supply"); while(1);}
+  if(isinf(calcR0)) {Serial.println("Warning: Connection issue, R0 is infinite (Open circuit detected) please check your wiring and supply"); while(1);}
+  if(calcR0 == 0){Serial.println("Warning: Connection issue found, R0 is zero (Analog pin shorts to ground) please check your wiring and supply"); while(1);}
   /*****************************  MQ CAlibration ********************************************/ 
   MQ4.serialDebug(true);
 }

examples/MQ-5/MQ-5.ino

@@ -65,7 +65,7 @@ void setup() {
   // Explanation: 
    // In this routine the sensor will measure the resistance of the sensor supposedly before being pre-heated
   // and on clean air (Calibration conditions), setting up R0 value.
-  // We recomend executing this routine only on setup in laboratory conditions.
+  // We recommend executing this routine only on setup in laboratory conditions.
   // This routine does not need to be executed on each restart, you can load your R0 value from eeprom.
   // Acknowledgements: https://jayconsystems.com/blog/understanding-a-gas-sensor
   Serial.print("Calibrating please wait.");
@@ -79,8 +79,8 @@ void setup() {
   MQ5.setR0(calcR0/10);
   Serial.println("  done!.");
   
-  if(isinf(calcR0)) {Serial.println("Warning: Conection issue, R0 is infinite (Open circuit detected) please check your wiring and supply"); while(1);}
-  if(calcR0 == 0){Serial.println("Warning: Conection issue found, R0 is zero (Analog pin shorts to ground) please check your wiring and supply"); while(1);}
+  if(isinf(calcR0)) {Serial.println("Warning: Connection issue, R0 is infinite (Open circuit detected) please check your wiring and supply"); while(1);}
+  if(calcR0 == 0){Serial.println("Warning: Connection issue found, R0 is zero (Analog pin shorts to ground) please check your wiring and supply"); while(1);}
   /*****************************  MQ CAlibration ********************************************/ 
   MQ5.serialDebug(true);
 }

examples/MQ-6/MQ-6.ino

@@ -65,7 +65,7 @@ void setup() {
   // Explanation: 
    // In this routine the sensor will measure the resistance of the sensor supposedly before being pre-heated
   // and on clean air (Calibration conditions), setting up R0 value.
-  // We recomend executing this routine only on setup in laboratory conditions.
+  // We recommend executing this routine only on setup in laboratory conditions.
   // This routine does not need to be executed on each restart, you can load your R0 value from eeprom.
   // Acknowledgements: https://jayconsystems.com/blog/understanding-a-gas-sensor
   Serial.print("Calibrating please wait.");
@@ -79,8 +79,8 @@ void setup() {
   MQ6.setR0(calcR0/10);
   Serial.println("  done!.");
   
-  if(isinf(calcR0)) {Serial.println("Warning: Conection issue, R0 is infinite (Open circuit detected) please check your wiring and supply"); while(1);}
-  if(calcR0 == 0){Serial.println("Warning: Conection issue found, R0 is zero (Analog pin shorts to ground) please check your wiring and supply"); while(1);}
+  if(isinf(calcR0)) {Serial.println("Warning: Connection issue, R0 is infinite (Open circuit detected) please check your wiring and supply"); while(1);}
+  if(calcR0 == 0){Serial.println("Warning: Connection issue found, R0 is zero (Analog pin shorts to ground) please check your wiring and supply"); while(1);}
   /*****************************  MQ CAlibration ********************************************/ 
   MQ6.serialDebug(true);
 }

examples/MQ-7/MQ-7.ino

@@ -72,7 +72,7 @@ void setup() {
   // Explanation: 
    // In this routine the sensor will measure the resistance of the sensor supposedly before being pre-heated
   // and on clean air (Calibration conditions), setting up R0 value.
-  // We recomend executing this routine only on setup in laboratory conditions.
+  // We recommend executing this routine only on setup in laboratory conditions.
   // This routine does not need to be executed on each restart, you can load your R0 value from eeprom.
   // Acknowledgements: https://jayconsystems.com/blog/understanding-a-gas-sensor
   Serial.print("Calibrating please wait.");
@@ -86,8 +86,8 @@ void setup() {
   MQ7.setR0(calcR0/10);
   Serial.println("  done!.");
   
-  if(isinf(calcR0)) {Serial.println("Warning: Conection issue, R0 is infinite (Open circuit detected) please check your wiring and supply"); while(1);}
-  if(calcR0 == 0){Serial.println("Warning: Conection issue found, R0 is zero (Analog pin shorts to ground) please check your wiring and supply"); while(1);}
+  if(isinf(calcR0)) {Serial.println("Warning: Connection issue, R0 is infinite (Open circuit detected) please check your wiring and supply"); while(1);}
+  if(calcR0 == 0){Serial.println("Warning: Connection issue found, R0 is zero (Analog pin shorts to ground) please check your wiring and supply"); while(1);}
   /*****************************  MQ CAlibration ********************************************/ 
   MQ7.serialDebug(true);
 }

examples/MQ-8/MQ-8.ino

@@ -66,7 +66,7 @@ void setup() {
   // Explanation: 
    // In this routine the sensor will measure the resistance of the sensor supposedly before being pre-heated
   // and on clean air (Calibration conditions), setting up R0 value.
-  // We recomend executing this routine only on setup in laboratory conditions.
+  // We recommend executing this routine only on setup in laboratory conditions.
   // This routine does not need to be executed on each restart, you can load your R0 value from eeprom.
   // Acknowledgements: https://jayconsystems.com/blog/understanding-a-gas-sensor
   Serial.print("Calibrating please wait.");
@@ -80,8 +80,8 @@ void setup() {
   MQ8.setR0(calcR0/10);
   Serial.println("  done!.");
   
-  if(isinf(calcR0)) {Serial.println("Warning: Conection issue, R0 is infinite (Open circuit detected) please check your wiring and supply"); while(1);}
-  if(calcR0 == 0){Serial.println("Warning: Conection issue found, R0 is zero (Analog pin shorts to ground) please check your wiring and supply"); while(1);}
+  if(isinf(calcR0)) {Serial.println("Warning: Connection issue, R0 is infinite (Open circuit detected) please check your wiring and supply"); while(1);}
+  if(calcR0 == 0){Serial.println("Warning: Connection issue found, R0 is zero (Analog pin shorts to ground) please check your wiring and supply"); while(1);}
   /*****************************  MQ CAlibration ********************************************/ 
   MQ8.serialDebug(true);
 }

examples/MQ-9-ALL/MQ-9-ALL.ino

@@ -55,7 +55,7 @@ void setup() {
   // Explanation: 
    // In this routine the sensor will measure the resistance of the sensor supposedly before being pre-heated
   // and on clean air (Calibration conditions), setting up R0 value.
-  // We recomend executing this routine only on setup in laboratory conditions.
+  // We recommend executing this routine only on setup in laboratory conditions.
   // This routine does not need to be executed on each restart, you can load your R0 value from eeprom.
   // Acknowledgements: https://jayconsystems.com/blog/understanding-a-gas-sensor
   Serial.print("Calibrating please wait.");
@@ -69,8 +69,8 @@ void setup() {
   MQ9.setR0(calcR0/10);
   Serial.println("  done!.");
   
-  if(isinf(calcR0)) {Serial.println("Warning: Conection issue, R0 is infinite (Open circuit detected) please check your wiring and supply"); while(1);}
-  if(calcR0 == 0){Serial.println("Warning: Conection issue found, R0 is zero (Analog pin shorts to ground) please check your wiring and supply"); while(1);}
+  if(isinf(calcR0)) {Serial.println("Warning: Connection issue, R0 is infinite (Open circuit detected) please check your wiring and supply"); while(1);}
+  if(calcR0 == 0){Serial.println("Warning: Connection issue found, R0 is zero (Analog pin shorts to ground) please check your wiring and supply"); while(1);}
   /*****************************  MQ CAlibration ********************************************/ 
   Serial.println("** Values from MQ-9 ****");
   Serial.println("|    LPG   |  CH4 |   CO  |");  

examples/MQ-9/MQ-9.ino

@@ -67,7 +67,7 @@ void setup() {
   // Explanation: 
    // In this routine the sensor will measure the resistance of the sensor supposedly before being pre-heated
   // and on clean air (Calibration conditions), setting up R0 value.
-  // We recomend executing this routine only on setup in laboratory conditions.
+  // We recommend executing this routine only on setup in laboratory conditions.
   // This routine does not need to be executed on each restart, you can load your R0 value from eeprom.
   // Acknowledgements: https://jayconsystems.com/blog/understanding-a-gas-sensor
   // ISSUE 44 - MQ9 needs a low/high temperature cycle like MQ7 #44
@@ -101,8 +101,8 @@ void setup() {
   MQ9.setR0(calcR0/10);
   Serial.println("  done!.");
   
-  if(isinf(calcR0)) {Serial.println("Warning: Conection issue, R0 is infinite (Open circuit detected) please check your wiring and supply"); while(1);}
-  if(calcR0 == 0){Serial.println("Warning: Conection issue found, R0 is zero (Analog pin shorts to ground) please check your wiring and supply"); while(1);}
+  if(isinf(calcR0)) {Serial.println("Warning: Connection issue, R0 is infinite (Open circuit detected) please check your wiring and supply"); while(1);}
+  if(calcR0 == 0){Serial.println("Warning: Connection issue found, R0 is zero (Analog pin shorts to ground) please check your wiring and supply"); while(1);}
   /*****************************  MQ CAlibration ********************************************/ 
   MQ9.serialDebug(true);
 }

examples/MQ-Board/MQ-Board.ino

@@ -103,7 +103,7 @@ void setup() {
   // Explanation: 
    // In this routine the sensor will measure the resistance of the sensor supposedly before being pre-heated
   // and on clean air (Calibration conditions), setting up R0 value.
-  // We recomend executing this routine only on setup in laboratory conditions.
+  // We recommend executing this routine only on setup in laboratory conditions.
   // This routine does not need to be executed on each restart, you can load your R0 value from eeprom.
   // Acknowledgements: https://jayconsystems.com/blog/understanding-a-gas-sensor
   Serial.print("Calibrating please wait.");
@@ -158,8 +158,8 @@ void setup() {
   Serial.print(MQ8calcR0/10); Serial.print(" | ");
   Serial.print(MQ9calcR0/10); Serial.println(" |");
 
-  if(isinf(MQ2calcR0) || isinf(MQ3calcR0) || isinf(MQ4calcR0) || isinf(MQ5calcR0)  || isinf(MQ6calcR0) || isinf(MQ7calcR0) || isinf(MQ8calcR0) || isinf(MQ9calcR0)) {Serial.println("Warning: Conection issue founded, R0 is infite (Open circuit detected) please check your wiring and supply"); while(1);}
-  if(MQ2calcR0 == 0 || MQ3calcR0 == 0 || MQ4calcR0 == 0 || MQ5calcR0 == 0 || MQ6calcR0 == 0 || MQ7calcR0 == 0 || MQ8calcR0 == 0 || MQ9calcR0 == 0){Serial.println("Warning: Conection issue founded, R0 is zero (Analog pin with short circuit to ground) please check your wiring and supply"); while(1);}
+  if(isinf(MQ2calcR0) || isinf(MQ3calcR0) || isinf(MQ4calcR0) || isinf(MQ5calcR0)  || isinf(MQ6calcR0) || isinf(MQ7calcR0) || isinf(MQ8calcR0) || isinf(MQ9calcR0)) {Serial.println("Warning: Connection issue found, R0 is infinite (Open circuit detected) please check your wiring and supply"); while(1);}
+  if(MQ2calcR0 == 0 || MQ3calcR0 == 0 || MQ4calcR0 == 0 || MQ5calcR0 == 0 || MQ6calcR0 == 0 || MQ7calcR0 == 0 || MQ8calcR0 == 0 || MQ9calcR0 == 0){Serial.println("Warning: Connection issue found, R0 is zero (Analog pin with short circuit to ground) please check your wiring and supply"); while(1);}
   /*****************************  MQ CAlibration ********************************************/ 
  
   //Print in serial monitor

examples/MQ135-ADS1115/MQ135-ADS1115.ino

@@ -62,8 +62,8 @@ void setup(void)
   MQ135.setR0(calcR0/10);
   Serial.println("  done!.");
 
-  if(isinf(calcR0)) {Serial.println("Warning: Conection issue, R0 is infinite (Open circuit detected) please check your wiring and supply"); while(1);}
-  if(calcR0 == 0){Serial.println("Warning: Conection issue found, R0 is zero (Analog pin shorts to ground) please check your wiring and supply"); while(1);}
+  if(isinf(calcR0)) {Serial.println("Warning: Connection issue, R0 is infinite (Open circuit detected) please check your wiring and supply"); while(1);}
+  if(calcR0 == 0){Serial.println("Warning: Connection issue found, R0 is zero (Analog pin shorts to ground) please check your wiring and supply"); while(1);}
   /*****************************  MQ CAlibration ********************************************/ 
   Serial.println("** Values from MQ-135 ****");
   Serial.println("|    CO   |  Alcohol |   CO2  |  Toluen  |  NH4  |  Aceton  |");  

examples/UnitTesting/UnitTesting.ino

@@ -27,11 +27,11 @@
 #define         Pin7                     (A7)  //Analog input 7 of your arduino
 #define         Pin8                     (A8)  //Analog input 8 of your arduino
 #define         Pin9                     (A9)  //Analog input 9 of your arduino
-#define         Pin10                    (A10) //Analog input 9 of your arduino
-#define         Pin11                    (A11) //Analog input 9 of your arduino
-#define         Pin12                    (A12) //Analog input 9 of your arduino
-#define         Pin13                    (A13) //Analog input 9 of your arduino
-#define         Pin14                    (A14) //Analog input 9 of your arduino
+#define         Pin10                    (A10) //Analog input 10 of your arduino
+#define         Pin11                    (A11) //Analog input 11 of your arduino
+#define         Pin12                    (A12) //Analog input 12 of your arduino
+#define         Pin13                    (A13) //Analog input 13 of your arduino
+#define         Pin14                    (A14) //Analog input 14 of your arduino
 #define         PWMPin                   (5)   // Pin connected to mosfet
 /***********************Software Related Macros************************************/
 #define         RatioMQ2CleanAir          (9.83) //RS / R0 = 9.83 ppm 

examples/external_A2D/external_A2D.ino

@@ -37,7 +37,7 @@
 //Definitions
 #define placa "Arduino UNO"
 #define Voltage_Resolution 5
-#define pin A0 //Analog input 0 -> This value can have any number, we recomend use A0
+#define pin A0 //Analog input 0 -> This value can have any number, we recommend use A0
 #define type "MQ-3 With A2D External connected" //MQ3
 #define ADC_Bit_Resolution 10 // Resolution of your external A2D
 #define RatioMQ3CleanAir 60   //RS / R0 = 60 ppm 
@@ -74,7 +74,7 @@ void setup() {
   // Explanation: 
    // In this routine the sensor will measure the resistance of the sensor supposedly before being pre-heated
   // and on clean air (Calibration conditions), setting up R0 value.
-  // We recomend executing this routine only on setup in laboratory conditions.
+  // We recommend executing this routine only on setup in laboratory conditions.
   // This routine does not need to be executed on each restart, you can load your R0 value from eeprom.
   // Acknowledgements: https://jayconsystems.com/blog/understanding-a-gas-sensor
   Serial.print("Calibrating please wait.");
@@ -89,8 +89,8 @@ void setup() {
   MQ3.setR0(calcR0/10);
   Serial.println("  done!.");
   
-  if(isinf(calcR0)) {Serial.println("Warning: Conection issue, R0 is infinite (Open circuit detected) please check your wiring and supply"); while(1);}
-  if(calcR0 == 0){Serial.println("Warning: Conection issue found, R0 is zero (Analog pin shorts to ground) please check your wiring and supply"); while(1);}
+  if(isinf(calcR0)) {Serial.println("Warning: Connection issue, R0 is infinite (Open circuit detected) please check your wiring and supply"); while(1);}
+  if(calcR0 == 0){Serial.println("Warning: Connection issue found, R0 is zero (Analog pin shorts to ground) please check your wiring and supply"); while(1);}
   /*****************************  MQ CAlibration ********************************************/ 
 
   MQ3.serialDebug(true);

examples/smokeDetector/smokeDetector.ino

@@ -59,7 +59,7 @@ void setup() {
   // Explanation: 
    // In this routine the sensor will measure the resistance of the sensor supposedly before being pre-heated
   // and on clean air (Calibration conditions), setting up R0 value.
-  // We recomend executing this routine only on setup in laboratory conditions.
+  // We recommend executing this routine only on setup in laboratory conditions.
   // This routine does not need to be executed on each restart, you can load your R0 value from eeprom.
   // Acknowledgements: https://jayconsystems.com/blog/understanding-a-gas-sensor
   Serial.print("Calibrating please wait.");
@@ -73,8 +73,8 @@ void setup() {
   MQ4.setR0(calcR0/10);
   Serial.println("  done!.");
   
-  if(isinf(calcR0)) {Serial.println("Warning: Conection issue, R0 is infinite (Open circuit detected) please check your wiring and supply"); while(1);}
-  if(calcR0 == 0){Serial.println("Warning: Conection issue found, R0 is zero (Analog pin shorts to ground) please check your wiring and supply"); while(1);}
+  if(isinf(calcR0)) {Serial.println("Warning: Connection issue, R0 is infinite (Open circuit detected) please check your wiring and supply"); while(1);}
+  if(calcR0 == 0){Serial.println("Warning: Connection issue found, R0 is zero (Analog pin shorts to ground) please check your wiring and supply"); while(1);}
   /*****************************  MQ CAlibration ********************************************/ 
   MQ4.serialDebug(true);
 }

keywords.txt

@@ -0,0 +1,29 @@
+MQUnifiedsensor KEYWORD1
+init KEYWORD2
+update KEYWORD2
+externalADCUpdate KEYWORD2
+setR0 KEYWORD2
+setRL KEYWORD2
+setA KEYWORD2
+setB KEYWORD2
+setRegressionMethod KEYWORD2
+setVoltResolution KEYWORD2
+setVCC KEYWORD2
+setPin KEYWORD2
+setADC KEYWORD2
+serialDebug KEYWORD2
+calibrate KEYWORD2
+readSensor KEYWORD2
+readSensorR0Rs KEYWORD2
+validateEcuation KEYWORD2
+getVoltage KEYWORD2
+setRsR0RatioGetPPM KEYWORD2
+getRS KEYWORD2
+stringTofloat KEYWORD2
+getA KEYWORD2
+getB KEYWORD2
+getR0 KEYWORD2
+getRL KEYWORD2
+getVoltResolution KEYWORD2
+getVCC KEYWORD2
+getRegressionMethod KEYWORD2

library.properties

@@ -1,5 +1,5 @@
 name=MQUnifiedsensor
-version=3.0.1
+version=3.0.3
 author= Miguel Califa <miguelangel5612@gmail.com>, Yersson Carrillo<miguelangel5612@gmail.com>, Ghiordy Contreras<miguelangel5612@gmail.com>
 maintainer= Miguel Califa <miguelangel5612@gmail.com>
 sentence= This library allows you to read the MQ sensors very easily.

src/MQUnifiedsensor.cpp

@@ -1,4 +1,6 @@
 #include "MQUnifiedsensor.h"
+#include <float.h>
+#include <math.h>
 
 #define retries 2
 #define retry_interval 20
@@ -21,11 +23,39 @@ void MQUnifiedsensor::init()
 {
   pinMode(_pin, INPUT);
 }
+static inline double safePow(double base, double exp){
+  if(exp == 0.0) return 1.0;
+  if(exp == 1.0) return base;
+  if(exp == 2.0) return base * base;
+  return pow(base, exp);
+}
+static inline bool willOverflow(double log_ppm){
+  static const double maxLog = log10((double)FLT_MAX);
+  static const double minLog = log10((double)FLT_MIN);
+  return (log_ppm > maxLog || log_ppm < minLog);
+}
+
 void MQUnifiedsensor::setA(float a) {
-  this->_a = a;
+  if(isinf(a) || isnan(a)) {
+    this->_a = 0;
+  } else if(a > MQ_MAX_A) {
+    this->_a = MQ_MAX_A;
+  } else if(a < -MQ_MAX_A) {
+    this->_a = -MQ_MAX_A;
+  } else {
+    this->_a = a;
+  }
 }
 void MQUnifiedsensor::setB(float b) {
-  this->_b = b;
+  if(isinf(b) || isnan(b)) {
+    this->_b = 0;
+  } else if(b > MQ_MAX_B) {
+    this->_b = MQ_MAX_B;
+  } else if(b < -MQ_MAX_B) {
+    this->_b = -MQ_MAX_B;
+  } else {
+    this->_b = b;
+  }
 }
 void MQUnifiedsensor::setR0(float R0) {
   this->_R0 = R0;
@@ -134,20 +164,23 @@ void MQUnifiedsensor::externalADCUpdate(float volt)
 }
 float MQUnifiedsensor::validateEcuation(float ratioInput)
 {
-  //Serial.print("Ratio input: "); Serial.println(ratioInput);
-  //Serial.print("a: "); Serial.println(_a);
-  //Serial.print("b: "); Serial.println(_b);
-  //Usage of this function: Unit test on ALgorithmTester example;
-  if(_regressionMethod == 1) _PPM= _a*pow(ratioInput, _b);
-  else 
-  {
-      // https://jayconsystems.com/blog/understanding-a-gas-sensor
-      double ppm_log = (log10(ratioInput)-_b)/_a; //Get ppm value in linear scale according to the the ratio value  
-      _PPM = pow(10, ppm_log); //Convert ppm value to log scale  
+  double ppm;
+  if(_regressionMethod == 1){
+      if(ratioInput <= 0 || _a == 0) return 0;
+      double logppm = log10((double)_a) + (double)_b * log10((double)ratioInput);
+      if(willOverflow(logppm)) ppm = (logppm > 0) ? FLT_MAX : 0.0;
+      else ppm = safePow(10.0, logppm);
   }
-  //Serial.println("Regression Method: "); Serial.println(_regressionMethod);
-  //Serial.println("Result: "); Serial.println(_PPM);
-  return _PPM;  
+  else
+  {
+      if(ratioInput <= 0 || _a == 0) return 0;
+      double logppm = (log10((double)ratioInput)-(double)_b)/(double)_a;
+      if(willOverflow(logppm)) ppm = (logppm > 0) ? FLT_MAX : 0.0;
+      else ppm = safePow(10.0, logppm);
+  }
+  if(isinf(ppm) || isnan(ppm)) ppm = FLT_MAX;
+  _PPM = (float)ppm;
+  return _PPM;
 }
 float MQUnifiedsensor::readSensor(bool isMQ303A, float correctionFactor, bool injected)
 {
@@ -161,16 +194,25 @@ float MQUnifiedsensor::readSensor(bool isMQ303A, float correctionFactor, bool in
   if(_RS_Calc < 0)  _RS_Calc = 0; //No negative values accepted.
   if(!injected) _ratio = _RS_Calc / this->_R0;   // Get ratio RS_gas/RS_air
   _ratio += correctionFactor;
-  if(_ratio <= 0)  _ratio = 0; //No negative values accepted or upper datasheet recomendation.
-  if(_regressionMethod == 1) _PPM= _a*pow(_ratio, _b); // <- Source excel analisis https://github.com/miguel5612/MQSensorsLib_Docs/tree/master/Internal_design_documents
-  else 
-  {
-    // https://jayconsystems.com/blog/understanding-a-gas-sensor <- Source of linear ecuation
-    double ppm_log = (log10(_ratio)-_b)/_a; //Get ppm value in linear scale according to the the ratio value  
-    _PPM = pow(10, ppm_log); //Convert ppm value to log scale  
+  if(_ratio <= 0)  _ratio = 0; //No negative values accepted or upper datasheet recommendation.
+  double ppm;
+  if(_regressionMethod == 1){
+    if(_ratio <= 0 || _a == 0) return 0;
+    double logppm = log10((double)_a) + (double)_b * log10((double)_ratio);
+    if(willOverflow(logppm)) ppm = (logppm > 0) ? FLT_MAX : 0.0;
+    else ppm = safePow(10.0, logppm);
   }
-  if(_PPM < 0)  _PPM = 0; //No negative values accepted or upper datasheet recomendation.
-  //if(_PPM > 10000) _PPM = 99999999; //No negative values accepted or upper datasheet recomendation.
+  else
+  {
+    if(_ratio <= 0 || _a == 0) return 0;
+    double logppm = (log10((double)_ratio)-(double)_b)/(double)_a;
+    if(willOverflow(logppm)) ppm = (logppm > 0) ? FLT_MAX : 0.0;
+    else ppm = safePow(10.0, logppm);
+  }
+  if(ppm < 0)  ppm = 0; //No negative values accepted or upper datasheet recommendation.
+  if(isinf(ppm) || isnan(ppm)) ppm = FLT_MAX;
+  _PPM = (float)ppm;
+  //if(_PPM > 10000) _PPM = 99999999; //No negative values accepted or upper datasheet recommendation.
   return _PPM;
 }
 float MQUnifiedsensor::readSensorR0Rs()
@@ -179,16 +221,25 @@ float MQUnifiedsensor::readSensorR0Rs()
   _RS_Calc = ((_VCC*_RL)/_sensor_volt)-_RL; //Get value of RS in a gas
   if(_RS_Calc < 0)  _RS_Calc = 0; //No negative values accepted.
   _ratio = this->_R0/_RS_Calc;   // Get ratio RS_air/RS_gas <- INVERTED for MQ-131 issue 28 https://github.com/miguel5612/MQSensorsLib/issues/28
-  if(_ratio <= 0)  _ratio = 0; //No negative values accepted or upper datasheet recomendation.
-  if(_regressionMethod == 1) _PPM= _a*pow(_ratio, _b); // <- Source excel analisis https://github.com/miguel5612/MQSensorsLib_Docs/tree/master/Internal_design_documents
-  else 
-  {
-    // https://jayconsystems.com/blog/understanding-a-gas-sensor <- Source of linear ecuation
-    double ppm_log = (log10(_ratio)-_b)/_a; //Get ppm value in linear scale according to the the ratio value  
-    _PPM = pow(10, ppm_log); //Convert ppm value to log scale  
+  if(_ratio <= 0)  _ratio = 0; //No negative values accepted or upper datasheet recommendation.
+  double ppm;
+  if(_regressionMethod == 1){
+    if(_ratio <= 0 || _a == 0) return 0;
+    double logppm = log10((double)_a) + (double)_b * log10((double)_ratio);
+    if(willOverflow(logppm)) ppm = (logppm > 0) ? FLT_MAX : 0.0;
+    else ppm = safePow(10.0, logppm);
   }
-  if(_PPM < 0)  _PPM = 0; //No negative values accepted or upper datasheet recomendation.
-  //if(_PPM > 10000) _PPM = 99999999; //No negative values accepted or upper datasheet recomendation.
+  else
+  {
+    if(_ratio <= 0 || _a == 0) return 0;
+    double logppm = (log10((double)_ratio)-(double)_b)/(double)_a;
+    if(willOverflow(logppm)) ppm = (logppm > 0) ? FLT_MAX : 0.0;
+    else ppm = safePow(10.0, logppm);
+  }
+  if(ppm < 0)  ppm = 0; //No negative values accepted or upper datasheet recommendation.
+  if(isinf(ppm) || isnan(ppm)) ppm = FLT_MAX;
+  _PPM = (float)ppm;
+  //if(_PPM > 10000) _PPM = 99999999; //No negative values accepted or upper datasheet recommendation.
   return _PPM;
 }
 float MQUnifiedsensor::calibrate(float ratioInCleanAir) {

src/MQUnifiedsensor.h

@@ -3,6 +3,12 @@
 
 #include <Arduino.h>
 #include <stdint.h>
+#include <float.h>
+#include <math.h>
+
+// Maximum coefficients allowed for the regression model
+#define MQ_MAX_A 1e30
+#define MQ_MAX_B 100.0
 
 /***********************Software Related Macros************************************/